The present invention relates to a linear guide device, and particularly a linear guide device in use for industrial machines and the like.
Further, the present invention also relates to a linear guide device including a slider in which spacers are each interposed between the rolling elements adjacent to each other in the circulating direction.
A conventional linear guide device of this type, as shown in FIG. 1, is provided with an axially extending guide rail 1 and a slider 2 slidably mounted on the guide rail 1.
Element rolling grooves 3, while linearly and axially extend, are formed on both sides of the guide rail 1. Element rolling grooves 31, which linearly extend (see FIG. 2), are formed in the inner side walls of sleeve parts 4 of a slider body 2A of the slider 2 in a state that the rolling element rolling grooves face the rolling element rolling grooves 3.
A number of steel balls B as rolling elements are rollably in a space defined between the rolling element rolling grooves 3 and 31 facing each other. The slider 2 is movable on and along the guide rail 1 through the rolling of the steel balls B. With its movement, the steel balls B interposed between the guide rail 1 and the slider 2 roll toward an end of the slider body 2A of the slider 2. To continuously move the slider 2 in the axial direction, it is necessary to endlessly move those steel balls B.
To this end, raceways 10 axially pass through the sleeve parts 4 of the slider body 2A, respectively. End caps 5 are provided at both ends of the slider body 2A. Element circulating R parts 6 (see FIG. 10), semicircularly curved, are formed in the end caps 5, while communicating with the space defined between the rolling element rolling grooves 3 and 31 and the raceways 10 (as a rolling element return passages). Those linear element raceways and the element circulating R parts are combined to form an element endless circulating raceway 7.
Thus, in the linear guide device, the element endless circulating raceway 7 includes the raceway 10, the spaces defined between the rolling element rolling grooves 3 and 31, and the curved element circulating R parts 6. A difference (which is maximized at a phase where a steel ball position reaches a tongue tip C) is present between a minute movement quantity dx1 and a minute movement quantity dx2 (FIG. 10). The minute movement quantity dx1 is a minute movement quantity of a rolling element when in the element endless circulating raceway 7, it moves from one space (load region) defined between the rolling element rolling grooves 3 and 31 to one (non-load region) of the curved element circulating R parts 6. The minute movement quantity dx2 is a minute movement quantity of another rolling element when it moves from the other curved element circulating R part 6 (non-load region) to the space (load region) defined between the rolling element rolling grooves 3 and 31 in accordance with the movement of the former rolling element by the minute movement quantity dx1. The difference causes a zig-zag motion of the steel balls and a great,-variation of dynamic frictional force to hinder a smooth revolving motion of the steel balls (their motion along the circulating raceway). This makes it difficult to improve the operability of the device. Reference is made to FIG. 11 to explain the cause to generate the difference between the minute movement quantities dx1 and dx2. When the center of a steel ball, which is on the linear part of the element endless circulating raceway 7, moves from a point A1 to another point A2, the center of another steel ball, which is on the curved part, moves from a point B1 to another point B2. It is geometrically clear that a movement quantity of the steel ball from A1 to A2 is different from a movement quantity of the steel ball from B1 to B2. This is the cause to generate the difference between the minute movement quantities dx1 and dx2.
This is one of problems in the conventional linear guide device.
As shown in FIG. 4, a spacer 9 having concave surfaces 8 on both side facing steel balls B located adjacent to each other in an element endless circulating raceway 7 is located such that the concave surfaces 8 of it are in contact with the adjacent steel balls B. JP-A-4-27405 discloses a technique to improve the operability. In the technique, some elastic spacers are each interposed between the adjacent rolling elements in the rolling element train. The elastic spacers function to absorb a gap or gaps which will be created in the circumferential direction in the rolling element train. JP-A-5-126148 discloses another technique in which to appropriately tighten the rolling element train, one of the spacers each interposed between the adjacent rolling elements is used to adjust the element-to-element pitch. The technique eliminates the gap that will be created in the rolling element train, and hence improves the operability.
In the conventional linear guide device, the element endless circulating raceway is constructed with a plurality of parts. To absorb the raceway length variation in the produces, caused by part machining error or the like, and to appropriately tighten the rolling element train, the spacer having a highly accurate and complicated configuration (e.g., a spacer having an elastic part or a movable part) is required. Manufacturing such a spacer is difficult. Since one or a plurality of spacers thus specified are used, the improvement of the operability is not satisfactory frequently.
When the raceway length variation is beyond an adjusting ability of the spacer, an excessive compression force acts on the rolling element train. As a result, the operability is considerably deteriorated, a harsh grating noise is generated.
This is the other of problems in the conventional linear guide device.